I'm not sure how it is simpler - using arctan instead of arcsin is just changing a button on the calculator. Again, the formula Glen gave looks more complicated than it needs to be because it was a computational formula (I think) for use in something like Matlab, whose arcsin function returns angle in radians, not degrees. On a calculator you don't need the 180/pi conversion factor.
Sure. You lay the razor flat on a table (as if honing), put one point of your callipers at the edge, and the other on the part of the spine that would touch the hone - this point usually has a bit of hone wear to guide you. That is measuring the hypotenuse.Quote:
Do you mind me asking how you measure the blade width from the top of the hone wear? I find doing this difficult. Thanks.
Edit: Here's a useful pictorial representation:
Attachment 111982
Yes, that is true. There are all sorts of other problems too, like measuring only at one point and assuming the hypotenuse/spine width ratio is constant for the entire blade. Then there are the smiling blades that have varying spine widths etc etc.Quote:
There is of course another problem with using any trigonometry to calculate the angle of the blade. we are assuming that the bevel is exactly half way between the spine width. What we are doing with both of these formulas is assuming that the bevel is central and multiplying the half of the bevel angle we calculate by 2.
There are a few interesting threads around about this. In particular, a post by an old member Mparker who mistakenly used arctan to calculate the angles, and subsequently fixed it up. The differences are not huge, but large enough.
James.